Some Studies That Piqued My Interest

Sulphoraphane is an inducer of phase II antioxidant and detoxification enzymes with anticancer properties [^31]

Sulphoraphane accumulates in cells - up to several hundred-fold over its extracellular concentration - by conjugation with intracellular GSH[^32].

Sulphoraphane has a protective effect against diabetic vascular complications (e.g., neuropathy)[^33]. One mechanism may be inhibition of the formation of advanced glycation end products (AGEs) and suppression of AGE-induced inflammatory reactions.

Sulforaphane Sources: Food vs Supplementation

The best results are probably obtained from ingesting sulphoraphane-rich foods rather than the isolated compound.

Many nootropic foods contain a blend of hundreds of compounds which enhances bioavailability and packs more of a punch than an isolated compound.

Case in point: PEITC is a compound also found in cruciferous vegetables and is thought to also have synergistic anti-inflammatory effects with sulforaphane[^25].

Top Dietary Sources of Sulphoraphane

Table 1. Glucosinolate Content of Selected Cruciferous Vegetables

Food (raw)

Serving

Total Glucosinolates (mg)

Brussels sprouts

½ cup (44 g)

104

Garden cress

½ cup (25 g)

98

Mustard greens

½ cup, chopped (28 g)

79

Turnip

½ cup, cubes (65 g)

60

Cabbage, savoy

½ cup, chopped (45 g)

35

Kale

1 cup, chopped (67 g)

67

Watercress

1 cup, chopped (34 g)

32

Kohlrabi

½ cup, chopped (67 g)

31

Cabbage, red

½ cup, chopped (45 g)

29

Broccoli

½ cup, chopped (44 g)

27

Horseradish

1 tablespoon (15 g)

24

Cauliflower

½ cup, chopped (50 g)

22

Bok choy (pak choi)

½ cup, chopped (35 g)

19

General Characteristics of Sulforaphane

Sulforaphane is a naturally-occurring compound belonging to the isothiocyanate group of organosulfur compounds.

It is present in relatively large quantities within cruciferous vegetables, such as broccoli. Brussels sprouts deliver 2x as much Glucosinolate (the precursor to sulphoraphane) than any other source.

Sulforaphane positively modulates cellular events and has a net-beneficial effect on bodily function. This article explores the effects of sulforaphane from food and supplementation has on the body.

Sources and Catabolism of Sulforaphane

In cruciferous vegetables, sulforaphane is found in the form of a prodrug known as glucoraphanin, where it is bound to a sugar moiety[^1].

When you chew a cruciferous vegetable, glucoraphanin is converted by Myrosinase into sulforaphane by cleaving the sugar group. Myrosinase is an enzyme present in the broccoli family of plants[^1].

In broccoli, sulforaphane is found in the following quantities:

Brocolli: 44-171mg/100g dry weight[^2]

Brocolli sprouts: 1153mg/100g dry weight[^2]

How to Take Sulforaphane Supplements

What's the ideal dosage of sulforaphane? Unfortunately, it's not well established, though we can hazard an educated guess.

Studies in animal models have shown supplementation of 0.1-0.5mg/kg sulforaphane to be biologically active[^3]. Based on these findings estimated human doses are as follows[^3]:

7-43mg for 150lb person

9-45mg for 200lb person

11-57 mg for 250lb person

You can obtain these doses of sulforaphane directly from cruciferous vegetables.

The effects of higher doses, while expected to be of further benefit, are not known[^3].

Another factor to take into account when considering taking sulforaphane supplements is the formulation.

Consumers are advised to use either an a-cyclodextrin inclusion or an SF-rich commercial supplement. That's because sulforaphane is more stable and bioavailable in these formulations[^3].

How Does the Body Handle Sulforaphane?

Once consumed, sulforaphane is well absorbed into the bloodstream via the small intestines. About 3/4 of the ingested dose is delivered into the bloodstream [^4].

Sulforaphane appears in the bloodstream 1 hour post-ingestion. Peak plasma levels are reached after 4 hours[^4]. The elimination half-life of sulforaphane is 2.2 hours and it becomes undetectable in blood 12 after consumption [^4].

Once in the bloodstream sulforaphane rapidly enters cells.

In the intracellular space, Sulforaphane interacts with glutathione, a cellular antioxidant, to form a glutathione-sulforaphane conjugate.

This process is catalyzed by the enzyme glutathione-s-transferase[^5]. Finally, once the glutathione-sulforaphane conjugate is formed, it exits the cell via the efflux protein MRP (Multidrug Resistance Protein), and to a lesser extent, P-glycoprotein[^5].

What are the Cellular Effects of Sulforaphane?

While the mechanism of action of Sulforaphane is not completely understood, Hydrogen Sulfide (H2S) likely plays a role.

H2S' main purpose in the body is to transmit chemical signals which bring about specific physiological or biochemical changes in a tissue or a cell.

The ability of sulforaphane to generate H2S lies in its isothiocyanate group (-N=C=S) which behaves as a sulfur donating molecule for its production[^6]. Interestingly, in prostatic cancer cell lines and in mouse liver cells, sulforaphane acts a potent generator of H2S[^7].

Neurological Effects

In neurons, sulforaphane is a potent inducer of Nrf-2 and an inhibitor of Nf-kB. Inducement of Nrf-2 and inhibition of Nf-kB protects against neurotoxicity and oxidative stress.

Due to its neuroprotective properties sulforaphane supplements could be of use in neurodegenerative disorders and for the management of neuropathic pain[^9]. In addition to its neuroprotective effects, sulpforaphane possesses anti-addictive properties whereby associated with reduced cocaine cravings in mice by inhibiting neuronal HDCA (Histone Deacetylase)[^10].

Anti-Aging Effects

Aging is associated with reduced Proteosomal activity and the build up to modified proteins in cells[^11].

Effects of Sulforaphane on Adipose tissue

Sulforaphane induces lipolysis. This is the processes where fat cells are broken down. This effect of sulofraphane is mediated by its ability to inhibit a protein known as AMPK which in turn enhances activity of the hormone sensitive lipase (HSL)[^13].

Effects on Skeletal Muscle

Sulforaphane acts on skeletal muscle by repressing a protein known as Myostatin.

Abolishment of Myostatin in the body results in muscle growth and reduction in fat mass. This effect of sulforaphane is the result of HDCA[^14] and Nrf2[^15] inhibition in myocytes.

Effects on Metabolism

Sulforaphane normalizes blood glucose and insulin sensitivity[^16]. However, the exact mechanism of this effect is unknown.

Effects on the Immune System

Sulforaphane posses potent anti-inflammatory properties by disrupting the generation of pro-inflammatory signals, an effect mediated by its ability to inhibit the action of NF-kB[^17].

Effects on Cancer Cells

This effect is most obvious in prostate[^7] and colorectal[^20] as it is able to reach these sites at sufficient amounts to produce anti-cancerous effects[^21].

Effects on Kidneys

Sulforaphane slows the progression of kidney disease by suppressing inflammation and oxidative stress. Once again, this effect is mediated by Nrf2[^22].

Does Sulforaphane Have Any Unwanted Effects?

Sulforaphane could theoretically harm the liver indirectly by increasing liver enzymes and cholesterol[^23].

Does Sulforaphane Interact with Other Substances?

Interaction with Curcumin

Synergistic effects are observed when sulforaphane is co-administered with curcumin in regard to its anti-inflammatory actions[^24].

Interaction with PhenylIsothiocyanate (PEITC)

PEITC is a compound also found in cruciferous vegetables. It has synergistic anti-inflammatory effects with sulforaphane[^25].

Interaction with Neoglucobrassicin

Neoglucobrassicin, an agent also found in cruciferous vegetables, may reduce the anti-oxidative properties of Sulforaphane by preventing its interaction with Nrf2[^26].

Interaction with Mustard

When directly consuming cruciferous vegetables, mustard increases the amount of sulforaphane entering the bloodstream by stabilizing the enzyme Myrosinase leading the production of more sulforaphane[^27].